Included setters in testing of the void => return-any-type feature.

The older issue #28939 did not
mention setters. They were already covered in the implementation, so
this CL just adds testing for it.

Addresses issue #29680.

[email protected], [email protected]

Review-Url: https://codereview.chromium.org/2899683003 .

Author: eernstg

tests/compiler/dart2js/type_checker_test.dart

@@ -100,6 +100,8 @@ Future testReturn(MockCompiler compiler) {
     check(returnWithType("void", 1), MessageKind.RETURN_VALUE_IN_VOID),
     check(returnWithType("void", null)),
     check(returnWithType("String", ""), MessageKind.RETURN_NOTHING),
+    check(arrowReturnWithType("void", "4")),
+    check("void set foo(x) => 5;"),
     // check("String foo() {};"), // Should probably fail.
   ]);
 }
@@ -2615,6 +2617,10 @@ String returnWithType(String type, expression) {
   return "$type foo() { return $expression; }";
 }
 
+String arrowReturnWithType(String type, expression) {
+  return "$type foo() => $expression;";
+}
+
 Node parseExpression(String text) =>
     parseBodyCode(text, (parser, token) => parser.parseExpression(token));
 

tests/language/void_arrow_return_test.dart

@@ -5,7 +5,9 @@
 // Testing that a void arrow function is allowed to return any type of value.
 
 void foo() => 42;
+void set bar(x) => 43;
 
 main() {
   foo();
+  bar = 44;
 }